Maxwellian mnemonic

del dot b is zero
del dot d is rho
del cross h is j and d-dot
del cross e is minus b-dot
and f is q-e and v cross b

In case you wonder what the "-dot" means.

(Try to read each hyphenated word as one syllable, so it rhymes properly, sort of.)

These are Maxwell equations and Lorentz force equation combined into a rhyme.